U.S. patent application number 11/117064 was filed with the patent office on 2006-11-02 for implantable optical pressure sensor for sensing urinary sphincter pressure.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Martin T. Gerber, Keith A. Miesel, Steven J. Shumaker.
Application Number | 20060247724 11/117064 |
Document ID | / |
Family ID | 37235481 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060247724 |
Kind Code |
A1 |
Gerber; Martin T. ; et
al. |
November 2, 2006 |
Implantable optical pressure sensor for sensing urinary sphincter
pressure
Abstract
The disclosure describes an optical fiber pressure sensor to
measure sphincter pressure which may be incorporated into a
therapeutic sphincter control system. The system senses sphincter
pressure and sends the information to a stimulator that is capable
of stimulation therapy to control sphincter contractility, thus
reducing unwanted urinary incontinence. Measuring sphincter
pressure is accomplished through the use of an optical fiber
connected to flexible tube section placed through the sphincter,
where properties of the emitted light are changed proportional to
the pressure on the tube section. The light is returned to a light
detector to measure light properties and create an electrical
signal representative of the pressure on the tube section. The
signal may then be sent by wireless telemetry to an implanted
stimulator or external programmer.
Inventors: |
Gerber; Martin T.; (Maple
Grove, MN) ; Miesel; Keith A.; (St. Paul, MN)
; Shumaker; Steven J.; (Woodbury, MN) |
Correspondence
Address: |
SHUMAKER & SIEFFERT, P. A.
8425 SEASONS PARKWAY
SUITE 105
ST. PAUL
MN
55125
US
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
37235481 |
Appl. No.: |
11/117064 |
Filed: |
April 28, 2005 |
Current U.S.
Class: |
607/41 ;
600/561 |
Current CPC
Class: |
A61N 1/36007 20130101;
A61B 5/202 20130101; A61B 5/205 20130101 |
Class at
Publication: |
607/041 ;
600/561 |
International
Class: |
A61N 1/00 20060101
A61N001/00; A61B 5/00 20060101 A61B005/00 |
Claims
1. An implantable electrical stimulation system comprising: an
implantable pressure sensor including an optical fiber, an emitter
that transmits light via the optical fiber, a detector that detects
reflected light via the optical fiber, circuitry that generates
pressure information based on the detected light, and a fixation
mechanism that positions the optical fiber proximate a sphincter
within a patient; and an implantable stimulator that delivers
electrical stimulation to the patient based on the pressure
information.
2. The system of claim 1, wherein the implantable pressure sensor
further includes a flexible tube section coupled to the optical
fiber, and a reflective, flexible diaphragm mounted within the
flexible tube section, wherein the diaphragm reflects the light
transmitted via the optical fiber, and deflects in response to
exertion of pressure against the flexible tube section by the
sphincter.
3. The system of claim 2, wherein the circuitry generates the
pressure information based on changes in one or more properties of
the reflected light in response to deflection of the diaphragm.
4. The system of claim 2 wherein the optical fiber includes a first
optical fiber that transmits the light from the emitter and a
second optical fiber that receives the light reflected by the
diaphragm.
5. The system of claim 2, wherein the optical fiber and the
flexible tube section have a combined length of less than
approximately 7 cm and the flexible tube section has an outer
diameter of approximately 1 to 3 mm.
6. The system of claim 1, wherein the implantable pressure sensor
includes a housing, the optical fiber extending from the housing,
and the fixation mechanism is positioned to attach the housing to
an inner wall of a bladder of the patient.
7. The system of claim 1, wherein the implantable sensor includes a
telemetry circuit that transmits the pressure information.
8. The system of claim 7, wherein the telemetry circuit transmits
the pressure information to the implantable stimulator, the
implantable stimulator adjusting one or more parameters of the
electrical stimulation based on the transmitted pressure
information.
9. The system of claim 7, further comprising an external programmer
to adjust stimulation parameters associated with the electrical
stimulation delivered by the implantable stimulator, wherein the
telemetry circuit transmits the pressure information to the
external programmer.
10. The system of claim 1, wherein the implantable pressure sensor
includes a sensor housing, wherein the optical fiber and flexible
tube section extend from the sensor housing, the system further
comprising a cystoscopic deployment device to deploy the
implantable pressure sensor, the deployment device defining a
cavity to carry the sensor housing and a channel to accommodate the
optical fiber and flexible tube section extending from the
housing.
11. A method comprising: transmitting light via an optical fiber
positioned proximate a sphincter within a patient; detecting
reflected light via the optical fiber; and generating pressure
information based on the detected light.
12. The method of claim 11, wherein the optical fiber is coupled to
a flexible tube section that contains a reflective, flexible
diaphragm mounted within the flexible tube section, and the
flexible tube section is mounted within the sphincter, wherein the
diaphragm reflects the light transmitted via the optical fiber, and
deflects in response to exertion of pressure against the flexible
tube section by the sphincter.
13. The method of claim 12, further comprising generating the
pressure information based on changes in one or more properties of
the reflected light in response to deflection of the diaphragm.
14. The method of claim 11, wherein the optical fiber includes a
first optical fiber that transmits the light and a second optical
fiber that receives the light reflected by the diaphragm.
15. The method of claim 11, wherein the optical fiber extends from
a housing, the method further comprising attaching the housing to a
bladder wall of the patient.
16. The method of claim 11, wherein the optical fiber is positioned
proximate a urinary sphincter of the patient.
17. The method of claim 11, further comprising adjusting one or
more parameters of electrical stimulation delivered to the patient
based on the pressure information.
18. The method of claim 11, further comprising cystoscopically
deploying the optical fiber within the urethra.
19. An implantable pressure sensor comprising: an optical fiber; an
emitter that transmits light via the optical fiber; a detector that
detects reflected light via the optical fiber; circuitry that
generates pressure information based on the detected light; and a
fixation mechanism that positions the optical fiber proximate a
sphincter within a patient.
20. The sensor of claim 19, wherein the implantable pressure sensor
further includes a flexible tube section coupled to the optical
fiber, and a reflective, flexible diaphragm mounted within the
flexible tube section, wherein the diaphragm reflects the light
transmitted via the optical fiber, and deflects in response to
exertion of pressure against the flexible tube section by the
sphincter.
21. The sensor of claim 20, wherein the circuitry generates the
pressure information based on changes in one or more properties of
the reflected light in response to deflection of the diaphragm.
22. The sensor of claim 20, wherein the optical fiber includes a
first optical fiber that transmits the light from the emitter and a
second optical fiber that receives the light reflected by the
diaphragm.
23. The sensor of claim 20, wherein the optical fiber and the
flexible tube section have a combined length of less than
approximately 7 cm and the flexible tube section has an outer
diameter of approximately 1 to 3 mm.
24. The sensor of claim 19, wherein the implantable pressure sensor
includes a housing, the optical fiber extending from the housing,
and the fixation mechanism is positioned to attach the housing to
an inner wall of a bladder of the patient.
25. The sensor of claim 19, wherein the implantable sensor includes
a telemetry circuit that transmits the pressure information.
26. The sensor of claim 19, further comprising a sensor housing,
wherein the optical fiber extends from the sensor housing, and
wherein the fixation mechanism includes a vacuum cavity defined by
the sensor housing and a pin that extends through tissue captured
in the vacuum cavity.
27. An implantable pressure sensor comprising: a sensor housing; an
optical fiber extending from the sensor housing; a flexible tube
section coupled to the optical fiber; a reflective, flexible
diaphragm within the flexible tube section; an emitter that
transmits light via the optical fiber to the diaphragm; a detector
that detects reflected light from the diaphragm the optical fiber;
circuitry that generates pressure information based on the detected
light; and a fixation mechanism that positions the optical fiber
proximate a sphincter within a patient, wherein the diaphragm
deflects in response to exertion of pressure against the flexible
tube section by the sphincter.
28. The sensor of claim 27, wherein the optical fiber includes a
first optical fiber that transmits the light from the emitter and a
second optical fiber that receives the light reflected by the
diaphragm.
29. The sensor of claim 27, wherein the optical fiber and the
flexible tube section have a combined length of less than
approximately 7 cm and the flexible tube section has an outer
diameter of approximately 1 to 3 mm.
30. The sensor of claim 27, further comprising a sensor housing,
wherein the optical fiber extends from the sensor housing, and
wherein the fixation mechanism includes a vacuum cavity defined by
the sensor housing and a pin that extends through tissue captured
in the vacuum cavity.
Description
TECHNICAL FIELD
[0001] The invention relates to implantable medical devices and,
more particularly, implantable sensors.
BACKGROUND
[0002] Urinary incontinence, or an inability to control urinary
function, is a common problem afflicting people of all ages,
genders, and races. Various muscles, nerves, organs and conduits
within the urinary tract cooperate to collect, store and release
urine. A variety of disorders may compromise urinary tract
performance and contribute to incontinence. Many of the disorders
may be associated with aging, injury or illness.
[0003] In some cases, urinary incontinence can be attributed to
improper sphincter function, either in the internal urinary
sphincter or external urinary sphincter. For example, aging can
often result in weakened sphincter muscles, which causes
incontinence. Some patients also may suffer from nerve disorders
that prevent proper triggering and operation of the bladder or
sphincter muscles. Nerves running though the pelvic floor stimulate
contractility in the sphincter. A breakdown in communication
between the nervous system and the urinary sphincter can result in
urinary incontinence.
[0004] Electrical stimulation of nerves in the pelvic floor may
provide an effective therapy for a variety of disorders, including
urinary incontinence. For example, an implantable neurostimulator
may be provided to deliver electrical stimulation to the sacral
nerve to induce sphincter constriction and thereby close or
maintain closure of the urethra at the bladder neck. An appropriate
course of neurostimulation therapy may be aided by a sensor that
monitors physiological conditions with the urinary tract. In some
cases, an implantable stimulation device may deliver stimulation
therapy based on the level or state of a sensed physiological
condition.
SUMMARY
[0005] The invention is directed to an implantable optical pressure
sensor for sensing urinary sphincter pressure, as well as a
neurostimulation system and method that make use of such a sensor
for alleviation of urinary incontinence. The sensor includes an
optical fiber and a flexible tube section. In some embodiments, the
flexible tube section may contain a reflective, flexible diaphragm.
The tube section is deployed within the bladder neck to transduce
urinary sphincter pressure as a function of pressure exerted on the
tube by the urinary sphincter. The optical fiber transmits light to
the diaphragm, which reflects light back into the optical fiber.
The diaphragm deflects under pressure exerted on the flexible tube
by the urinary sphincter. As a result, optical properties of the
light reflected by the diaphragm change, indicating a change in
urinary sphincter pressure.
[0006] Inadequate sphincter pressure may result in involuntary
bladder voiding, i.e., incontinence. The optical pressure sensor
may provide short- or long-term monitoring of urinary sphincter
pressure, e.g., for analysis by a clinician. Alternatively, the
optical pressure sensor may form part of a closed-loop
neurostimulation system. For example, neurostimulation therapy can
be applied to increase sphincter pressure, and thereby prevent
involuntary urine leakage. In particular, an implantable
neurostimulator may be responsive to urinary sphincter pressure
signals generated by the optical pressure sensor, as described
herein, to provide closed loop neurostimulation therapy to
alleviate incontinence.
[0007] In one embodiment, the invention provides an implantable
electrical stimulation system comprising an implantable pressure
sensor including an optical fiber, an emitter that transmits light
via the optical fiber, a detector that detects reflected light via
the optical fiber, circuitry that generates pressure information
based on the detected light, and a fixation mechanism that
positions the optical fiber proximate a sphincter within a patient,
and an implantable stimulator that delivers electrical stimulation
to the patient based on the pressure information.
[0008] In another embodiment, the invention provides a method
comprising transmitting light via an optical fiber positioned
proximate a sphincter within a patient, detecting reflected light
via the optical fiber, and generating pressure information based on
the detected light.
[0009] In an additional embodiment, the invention provides an
implantable pressure sensor comprising an optical fiber, an emitter
that transmits light via the optical fiber, a detector that detects
reflected light via the optical fiber, circuitry that generates
pressure information based on the detected light, and a fixation
mechanism that positions the optical fiber proximate a sphincter
within a patient.
[0010] In a further embodiment, the invention provides an
implantable pressure sensor comprising a sensor housing, an optical
fiber extending from the sensor housing, a flexible tube section
coupled to the optical fiber, a reflective, flexible diaphragm
within the flexible tube section, an emitter that transmits light
via the optical fiber to the diaphragm, a detector that detects
reflected light from the diaphragm the optical fiber, circuitry
that generates pressure information based on the detected light,
and a fixation mechanism that positions the optical fiber proximate
a sphincter within a patient, wherein the diaphragm deflects in
response to exertion of pressure against the flexible tube section
by the sphincter.
[0011] Although the invention may be especially applicable to
sensing urinary sphincter pressure, the invention alternatively may
be applied more generally to other sphincters within the patient,
such as the lower esophageal sphincter (LES) or pyloric sphincter.
In addition, in those instances, the invention may be adapted to
support electrical stimulation of other body organs, such as the
stomach or intestines, e.g., for treatment of obesity or gastric
mobility disorders.
[0012] In various embodiments, the invention may provide one or
more advantages. For example, the use of a thin, flexible optical
pressure sensor permits pressure to be sensed within the narrow,
constricted passage proximate the urinary sphincter. In this
manner, pressure can be sensed without significantly obstructing or
altering the physiological function or the urinary sphincter.
[0013] The optical pressure sensor may be coupled to a larger
sensor housing that resides within the bladder and houses sensor
electronics for emitting and detecting light to measure the
pressure on the tube. The optical pressure sensor permits pressure
information to be obtained on a continuous or periodic basis as the
patient goes about a daily routine. In addition, the flexible
nature of the tube permits the sensor to be implanted in a variety
of locations, and to be constructed in variety of shapes and
sizes.
[0014] The optical pressure sensor may transmit sensed pressure
information to an implantable stimulator to permit dynamic control
of the therapy delivered by the stimulator on a closed-loop basis.
For example, the stimulator may adjust stimulation parameters, such
as amplitude, pulse width or pulse rate, in response to the sensed
pressure. In this manner, the stimulator can provide enhanced
efficacy and prevent involuntary leakage. In addition, or
alternatively, adjustment may involve on and off cycling of the
stimulation in response to pressure levels indicative of a
particular bladder fill stage. For example, stimulation may be
turned off until the pressure level exceeds a threshold indicative
of a particular fill stage of the bladder. Also, with closed-loop
stimulation, the stimulator may generate stimulation parameter
adjustments that more effectively target the function of the
urinary sphincter muscle, thereby enhancing stimulation efficacy.
In some patients, more effective stimulation via the sacral nerve
may actually serve to strengthen the sphincter muscle, restoring
proper operation.
[0015] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram illustrating an implantable
stimulation system, incorporating urinary sphincter pressure
sensor, for alleviation of urinary incontinence.
[0017] FIG. 2 is an enlarged schematic diagram illustrating an
implantable pressure sensor with an optical tube extending through
the urinary sphincter of a patient.
[0018] FIG. 3 is an enlarged, cross-sectional side view of the
implantable pressure sensor of FIGS. 1 and 2.
[0019] FIG. 4 is a schematic diagram illustrating placement of an
implantable pressure sensor with an optical tube extending through
the internal urinary sphincter of a patient.
[0020] FIG. 5 is functional block diagram illustrating various
components of an exemplary implantable pressure sensor.
[0021] FIG. 6 is a functional block diagram illustrating various
components of an implantable stimulator.
[0022] FIG. 7 is a schematic diagram illustrating cystoscopic
deployment of an implantable pressure sensor via the urethra.
[0023] FIG. 8 is a schematic diagram illustrating retraction of a
deployment device upon fixation of a pressure sensor within a
patient's urinary tract.
[0024] FIG. 9 is a cross-sectional side view of a deployment device
during deployment and fixation of a pressure sensor.
[0025] FIG. 10 is a cross-sectional bottom view of the deployment
device of FIG. 10 before attachment of the pressure sensor.
[0026] FIG. 11 is a flow diagram illustrating a technique for
delivery of stimulation therapy based on closed loop feedback from
an implantable pressure sensor.
DETAILED DESCRIPTION
[0027] FIG. 1 is a schematic diagram illustrating an implantable
stimulation system 10 for alleviation of urinary incontinence. As
shown in FIG. 1, system 10 includes an implantable optical pressure
sensor 12, implantable stimulator 14 and external programmer 16
shown in conjunction with a patient 18. Pressure sensor 12 senses a
pressure level exerted by urinary sphincter 22 on urethra 20
proximate the neck 23 of bladder 24, and transmits pressure
information based on the sensed pressure level to at least one of
stimulator 14 and programmer 16 by wireless telemetry. Stimulator
14 or programmer 16 may record the information, generate
adjustments to electrical stimulation parameters applied by the
stimulator, or both.
[0028] FIG. 2 is an enlarged schematic diagram illustrating
implantable optical pressure sensor 12. As shown in FIGS. 1 and 2,
pressure sensor 12 includes a sensor housing 26, an optical fiber
28, and a flexible tube section 30. Flexible tube section 30 is
positioned for engagement with urinary sphincter 22, and is sealed
from the environment. Tube section 30 contains a reflective,
flexible diaphragm that deflects in response to pressure changes
within the tube section. Tube section 30 may be filled with air or
other optically transmissive media. Optical fiber 28 transmits
light to the diaphragm and receives reflected light from the
diaphragm. When the diaphragm deflects, the properties of the
reflected light change, indicating a change in pressure within the
flexible tube and, in turn, a change in the pressure of urinary
sphincter 22.
[0029] Sensor housing 26 contains a light emitter that transmits
light through optical fiber 28 and a light detector that detects
the reflected light received from the optical fiber, as will be
described in further detail. The light emitter and detector are
positioned adjacent to a proximal end of optical fiber 28. If a
single optical fiber is used for both transmission of light and
reception of reflected light, an optical coupling element may be
provided in sensor housing 26 to couple the emitter and detector to
the optical fiber 28. In other embodiments, separate optical fibers
can be used for transmission or reception. In either case, the
light detector generates an output signal that varies according to
the properties of the reflected light. Sensor housing 26 further
includes electronics to generate pressure information based on the
output signal, and telemetry circuitry for wireless transmission of
the information to stimulator 14, programmer 16 or both.
[0030] As further shown in FIGS. 1 and 2, sensor housing 26 may
reside within bladder 24. Sensor housing 26 may be temporarily or
permanently attached to an inner wall 27 of bladder 24, such has
the mucosal lining, as will be described. Alternatively, housing 26
may be implanted sub-mucosally. Optical fiber 28 extends away from
sensor housing 26 and through an inner lumen defined by the bladder
neck proximate urinary sphincter 22. In this manner, flexible tube
section 30 is positioned to directly sense the pressure level
exerted by urinary sphincter 22. Yet, optical fiber 28 and tube
section 30 may be sufficiently thin to avoid significant
obstruction of urethra 20 or disruption of the function of urinary
sphincter.
[0031] As a further alternative, housing 26 may reside outside
bladder 24, in which case optical fiber 28 and tube section 30 may
extend into bladder 24 and through urinary sphincter 22 through a
hole formed in the bladder. In this case, housing 26 may be
surgically or laparoscopically implanted within the abdomen. Fiber
28 and tube section 30 may be surgically or laparoscopically guided
through a hole in the wall of bladder 24. A cystoscope may be used
to grab tube section 30 and pull it downward through urinary
sphincter 22 and urethra 20. In some embodiments, housing 26 and
its contents may be integrated with stimulator 14, in which case
optical fiber 28 and tube section 30 extends from the stimulator
housing and into bladder 24, much like leads carrying stimulation
or sense electrodes
[0032] With further reference to FIG. 1, implantable stimulator 14
includes an electrical lead 15 (partially shown in FIG. 1) carrying
one or more electrodes that are placed at a nerve site within the
pelvic floor. For example, the electrodes may be positioned to
stimulate the sacral nerve and thereby innervate urinary sphincter
22. In particular, electrical stimulation may be applied to cause
urinary sphincter 22 to increase closing pressure to avoid
involuntary leakage from bladder 24. Alternatively, if voluntary
voiding is desired by patient 18, electrical stimulation may be
suspended or reduced to reduce the closing pressure exerted by
urinary sphincter 22 on urethra 20 at the bladder neck.
[0033] For spinal cord injury patients who cannot perceive a
sensation of bladder fullness, sphincter pressure sensed by
pressure sensor 12 may be transmitted to external programmer 16,
with or without an accompanying stimulator 14, to advise the
patient when urinary sphincter pressure is high, indicating bladder
fullness. In this case, the advice may be in the form of a audible,
visual or vibratory stimulus. In response to the advice, the spinal
cord injury patient is able to catheterize the urethra 20 and
bladder 24 to voluntarily relieve urine.
[0034] Implantable stimulator 14 delivers stimulation therapy to
the sacral nerve in order to keep the sphincter 22 constricted and
keep contents of bladder 24 from leaking out through urethra 20. At
predetermined times or at patient controlled instances, the
external programmer 16 may program stimulator 14 to interrupt the
stimulation to allow the sphincter to relax, thus permitting
voiding of bladder 24. Upon completion of the voiding event,
external programmer 16 may program stimulator 14 to resume
stimulation therapy and thereby maintain closure of urinary
sphincter 22.
[0035] In addition, adjustment of stimulation parameters may be
responsive to pressure information transmitted by implantable
optical pressure sensor 12. For example, external programmer 16 or
implantable stimulator 14 may adjust stimulation parameters, such
as amplitude, pulse width, and pulse rate, based on pressure
information received from implantable sensor 12. In this manner,
implantable stimulator 14 adjusts stimulation to either increase or
reduce urinary sphincter pressure based on the actual pressure
level exerted by urinary sphincter 22.
[0036] Pressure sensor 12 may transmit pressure information
periodically, e.g., every few seconds, minutes or hours. In some
embodiments, pressure sensor 12 may transmit pressure information
when there is an abrupt change in sphincter pressure, e.g., a
pressure change that exceeds a predetermined threshold. In addition
to parameter adjustments, or alternatively, adjustment may involve
on and off cycling of the stimulation in response to pressure
levels indicative of a particular bladder fill stage. For example,
stimulation may be turned off until the pressure level exceeds a
threshold indicative of a particular fill stage of the bladder, at
which time stimulation is turned on. Then, stimulation parameters
may be further adjusted as the sensed pressure level changes.
[0037] External programmer 16 may be a small, battery-powered,
portable device that accompanies the patient 18 throughout a daily
routine. Programmer 16 may have a simple user interface, such as a
button or keypad, and a display or lights. Patient 18 may initiate
a voiding event, i.e., a voluntary voiding of bladder 24, via the
user interface. In some embodiments, the length of time for a
voiding event may be determined by pressing and holding down a
button for the duration of a voiding event, pressing a button a
first time to initiate voiding and a second time when voiding is
complete, or by a predetermined length of time permitted by
programmer 16 or implantable stimulator 14. In each case,
programmer 16 causes implantable stimulator 14 to temporarily
terminate stimulation so that voluntary voiding is possible.
[0038] In some embodiments, stimulator 14 may immediately
recommence stimulation upon completion of a voiding event, and
thereafter adjust stimulation parameters based on pressure
information generated by implantable sensor 12. Alternatively,
stimulator 14 may terminate stimulation upon initiation of a
voiding event, and recommence stimulation only after implantable
pressure sensor 12 measures a decrease of pressure in the urethra
20 that corresponds to bladder 24 being empty. As a further
alternative, following completion of the voiding event, stimulator
14 may wait to recommence stimulation until pressure sensor 12
detects generation of an inadequate pressure level by urinary
sphincter 22, which could result in involuntary leakage. In this
case, stimulator 14 recommences stimulation to enhance urinary
sphincter pressure.
[0039] Implantable stimulator 14 may be constructed with a
biocompatible housing, such as titanium or stainless steel, or a
polymeric material such as silicone or polyurethane, and surgically
implanted at a site in patient 18 near the pelvis. The implantation
site may be a subcutaneous location in the side of the lower
abdomen or the side of the lower back. One or more electrical
stimulation leads 15 are connected to implantable stimulator 14 and
surgically or percutaneously tunneled to place one or more
electrodes carried by a distal end of the lead at a desired nerve
site, such as a sacral nerve site within the sacrum.
[0040] In the example of FIGS. 1 and 2, sensor housing 26 of
implantable pressure sensor 12 is attached to the inner wall 27 of
bladder 24 near bladder neck 23. However, the attachment site for
sensor housing 26 could be anywhere with access to urinary
sphincter 22. With a relatively long optical fiber 28, for example,
sensor housing 26 could be positioned at a greater distance from
bladder neck 23. Also, in some embodiments, sensor housing 26 could
be attached within urethra 20, e.g., downstream from urinary
sphincter 22, although attachment of the sensor housing within
bladder 24 may be desirable to avoid obstruction of the
urethra.
[0041] FIG. 3 is an enlarged, cross-sectional side view of the
implantable pressure sensor 12 of FIGS. 1 and 2. As shown in FIG.
3, sensor housing 26 receives the proximal end of flexible optical
fiber 28. A sensing element 34 is mounted within sensor housing 26
to sense a urinary sphincter pressure level via optical fiber 28.
Sensing element 34 may be coupled to a circuit board 38 within
sensor housing 26, and includes an optical emitter 35 and a
detector 37. Optical emitter 35 may be a light emitting diode
(LED). Detector 37 may be a photodiode. In the example of FIG. 3,
optical fiber 28 includes two optical fibers, i.e., a transmit
fiber 39 coupled to emitter 35 and a receive fiber 41 coupled to
optical detector 41. Each optical fiber 39, 41 extends into
flexible tube section 30.
[0042] Sensor housing 26 may be made from a biocompatible material
such as titanium, stainless steel or nitinol, or a polymeric
material such as silicone or polyurethane. Another material for
fabrication of sensor housing 26 is a two-part epoxy. An example of
a suitable epoxy is a two-part medical implant epoxy manufactured
by Epoxy Technology, Inc., mixed in a ratio of 10 grams of resin to
one gram of activator. In general, sensor housing 26 contains no
external openings, with the exception of the opening to receive
optical fiber 28, thereby protecting sensing element 26 and circuit
board 38 from the environment within bladder 24. The proximal end
of optical fiber 28 resides within sensor housing 26 while the
distal end resides outside of the sensor housing. The opening in
sensor housing 26 that receives the proximal end of optical fiber
28 may be sealed to prevent exposure of interior components.
[0043] The core and cladding of optical fiber 28 may be formed from
any of a variety of conventional glass or polymeric materials. In
addition, single mode or multi-mode fibers may be selected. In some
embodiments, a protective, a flexible sheath (not shown) may be
formed over optical fiber 28. The flexibility of optical fiber 28
permits it to bend and conform to contours within bladder neck 23,
facilitating placement of flexible tube section 30 within urethra
20 proximate urinary sphincter 22.
[0044] Flexible tube section 30 may be formed from any of a variety
of flexible, biocompatible materials such as polyurethane or
silicone. The material should be sufficiently flexible to permit
deform in response to pressure exerted on urethra 20 by urinary
sphincter 22 at bladder neck 23. Flexible tube section 30
preferably is sealed to define a compartment. so that deformation
produces volumetric changes and pressure changes within the
compartment. Accordingly, flexible tube section 30 may have a
closed distal end and a sealed proximal end that is sealed about
fiber 28. The compartment may contain a gaseous medium such as air.
During operation, urinary sphincter 22 exerts pressure inward
against the outer wall of urethra 20. In turn, the inner wall of
urethra 20 exerts pressure inward against the outer wall of
flexible tube section 30, causing the wall of the tube section to
deform and compress inward. In some embodiments, flexible tube
section 30 may be coated to avoid calcification.
[0045] Inward deformation of flexible tube section 30 causes a
mechanical deflection of the membrane mounted inside. As light is
transmitted onto the membrane by optical fiber 39, some of the
reflected light received by optical fiber 41 is refracted to a
varying degree based upon the deformation of the membrane. When the
reflected light is detected by light detector 37, the light
detector generates an output signal that is influenced by the
physical properties of the detected light. Circuitry within sensing
element generates pressure information based on the reflected light
detected by detector 37.
[0046] The physical property may be simply an intensity of the
received light, which is influenced by the degree of deflection of
the membrane. In this case, an increase or decrease in the
intensity of reflected light can be use to produce a urinary
sphincter pressure level. Alternatively, physical property may be a
wavelength of the reflected light, relative to a wavelength of the
transmitted light. As the membrane deflects, changes in the
wavelength of the reflected light can be used to produce a urinary
sphincter pressure level. In other embodiments, the membrane may be
formed with an interference pattern or grating that aids in
wavelength differentiation between the reflected light and the
transmitted light. Based upon the differences in amplitude,
wavelength, or other optical properties, sensing element 34
generates a pressure signal that represents the pressure on
flexible tube section 30. Electronics on circuit board 38 generate
pressure information based on the pressure signal.
[0047] Optical fiber 28 and flexible tube section 30 may be
provided with different dimensions selected for patients having
different anatomical dimensions. In particular, implantable
pressure sensor 12 may be constructed with an optical fiber 28 and
flexible tube section 30 having different lengths and diameters.
Different tube lengths may be necessary given the distance between
the attachment site of sensor housing 26 and urinary sphincter 22,
either to ensure that flexible tube section 30 reaches the
sphincter or does not extend too far down urethra 20. Multiple
diameters may also be necessary to allow a dysfunctional sphincter
22 to close completely or to allow optical fiber 28 and flexible
tube section 30 to be placed into a narrow urethra 20. The
dimensions may be fixed for a given pressure sensor 12, as a
complete assembly. Alternatively, fluid tubes of different sizes
may be attached to a pressure sensor housing 26 by a physician
prior to implantation.
[0048] In general, for male patients, optical fiber 28 and tube
section 30 may have a combined length of less than approximately 9
cm and more preferably less than approximately 7 cm. For female
patients, optical fiber 28 and tube section 30 may have a combined
length f less than approximately 7 cm and more preferably less than
approximately 5 cm. In some embodiments, optical fiber 28 and tube
section 30 may have a combined length of approximately 0.5 cm to 3
cm. The length of optical fiber 28 and tube section 30 may vary
according to the anatomy of the patient, and may vary between male,
female and pediatric patients. In addition, tube 30 may have an
outer diameter in a range of approximately 1 to 3 mm. The wall of
tube 30 may be relatively thin to ensure sufficient deformation and
conformability, yet thick enough to ensure structural integrity. As
an example, the thickness of the wall of tube 30 may be in a range
of approximately 0.1 mm to 0.3 mm.
[0049] Attaching implantable pressure sensor 12 to the mucosal
lining of bladder 24 may be accomplished in a variety of ways, but
preferably is completed in a manner that will not excessively
injure bladder 24. Preferably, attachment should cause limited
inflammation no adverse physiological modification, such as tissue
infection or a loss in structural integrity of bladder 24. However,
it is desirable that implantable pressure sensor 12 also be
attached securely to the attachment site in order to provide an
extended period of measurement without prematurely loosening or
detaching from the intended location.
[0050] As an example, sensor housing 26 may contain a vacuum cavity
39 that permits a vacuum to be drawn by a vacuum channel 40. The
vacuum is created by a deployment device having a vacuum line in
communication with vacuum channel 40. The vacuum draws a portion 42
of the mucosal lining 44 of bladder 24 into vacuum cavity 39. Once
the portion 42 of mucosal lining 44 is captured within vacuum
cavity 39, a fastening pin 46 is driven into the captured tissue to
attach sensor housing 26 within bladder 24. Fastening pin 46 may be
made from, for example, stainless steel, titanium, nitinol, or a
high density polymer. The shaft of pin 46 may be smooth or rough,
and the tip may be a sharp point to allow for easy penetration into
tissue. Fastening pin 46 may be driven into housing 26 and the
portion 42 of mucosal lining 44 under pressure, or upon actuation
by a push rod, administered by a deployment device.
[0051] In some embodiments, fastening pin 46 may be manufactured
from a degradable material that the breaks down over time, e.g. in
the presence of urine, to release implantable pressure sensor 12
within a desired time period after attachment. In still another
embodiment, implantable pressure sensor 12 may be attached without
the use of a penetrating rod but with a spring-loaded clip to pinch
trapped mucosal lining 44 within cavity 39. A variety of other
attachment mechanisms, such as pins, clips, barbs, sutures, helical
screws, surgical adhesives, and the like may be used to attach
sensor housing 26 to mucosal lining 44 of bladder 24.
[0052] FIG. 4 is a schematic diagram illustrating placement of an
implantable pressure sensor 12 with a flexible optical fiber 28
extending through the urinary sphincter 22 of a patient 18. FIG. 4
also illustrates flexible tube section 30 in greater detail. In the
example of FIG. 4, optical fiber 28, including transmit fiber 39
and receive fiber 41, leaves bladder 24 through bladder neck 23 and
passes through internal urinary sphincter 22 as it enters urethra
20. In general, sphincter 22 is an annulus shaped muscle that
surrounds the portion of urethra 20 below bladder neck 23 and
constricts to make the urethral walls meet and thereby close
urethra 20 to prevent involuntary urine leakage from bladder 24.
Upon constriction of sphincter 22, the walls of urethra 20 close
onto flexible tube section 30 of optical fiber 28 to increase the
internal pressure of the tube section, which provides a measurement
of the closing pressure of sphincter 22.
[0053] As further shown in FIG. 4, flexible diaphragm 43 is mounted
within flexible tube section 30 below optical fibers 39, 41.
Flexible diaphragm 43 includes an optically reflective surface on a
side facing optical fibers 39, 41. In this manner, light
transmitted via optical fiber 39 is reflected by diaphragm 43 and
received via optical fiber 41. Flexible diaphragm may be
substantially circular and bonded at its edges to an inner wall of
flexible tube section 30. For example, flexible diaphragm may be
bonded to the inner wall of flexible tube section 30 by adhesives,
ultrasonic welding, or other techniques. In some embodiments, tube
section 30 may include an annular mounting ledge or other
equivalent mounting structures to support at least an outer edge of
the diaphragm 43. Flexible diaphragm 43 may be formed from any of a
variety of flexible materials. The materials may be reflective.
Alternatively, a reflective coating may be formed on diaphragm 43,
e.g., by vapor deposition, sputtering, dip coating, roll coating or
the like.
[0054] Because optical fiber 28 and flexible tube section 30 have
circular cross-sections and a small diameter, a closed sphincter 22
will still be able to substantially seal urethra 20 around optical
fiber 28, flexible tube section 30, or both. When sphincter 22 is
relaxed, in some embodiments, implantable pressure sensor 12 may be
used to measure the pressure of fluid in urethra 20. The open
sphincter 22 allows urine to be passed out of the urethra and
patient 18. Optical fiber 28 is under the same pressure as the
urethra and can allow implantable pressure sensor 12 to measure
this urethral pressure. This may allow monitoring of urinary
dysfunctions due to pressure during voiding events and may also be
used by implantable stimulator 14 to detect the end of a voiding
event by measuring decrease of urethral pressure as an indication
of reduced urine flow.
[0055] As shown in FIG. 4, the placement of optical fiber 28 and
flexible tube section 30 does not significantly interfere with
normal bladder function. Bladder function is unimpaired and fluid
flow to urethra 20 can occur normally, as flexible tube section 30
allows enough room for urine to pass and exit bladder 24 via
urethra 20. Due to varying sizes and shapes of patient anatomy,
optical fiber 28 and flexible tube section 30 may be manufactured
in a variety of lengths and diameters.
[0056] FIG. 5 is functional block diagram illustrating various
components of an exemplary implantable pressure sensor 12. In the
example of FIG. 5, implantable pressure sensor 12 includes a
sensing element 34, processor 48, memory 50, telemetry interface
52, and power source 54. Sensing element 34 transforms measured
changes in emitted light from optical fiber 28 into electrical
signals representative of closing pressure of urinary sphincter 22.
Again, optical fiber 28 may include a transmit fiber 39 and a
receive fiber 41, or a single fiber with an optical coupler for
optical coupling to emitter 35 and detector 37. The electrical
signals may be amplified, filtered, and otherwise processed as
appropriate by electronics within sensor 12. In particular, sensor
12 may include circuitry to detect changes in light intensity or
wavelength. In some embodiments, the signals may be converted to
digital values and processed by processor 48 before being saved to
memory 50 or sent to implantable stimulator 14 as pressure
information via telemetry interface 52.
[0057] Memory 50 stores instructions for execution by processor 48
and pressure information generated by sensing element 36. Pressure
data may then be sent to implantable stimulator 14 or external
programmer 16 for long-term storage and retrieval by a user. Memory
50 may include separate memories for storing instructions and
pressure information. In addition, processor 48 and memory 50 may
implement loop recorder functionality in which processor 48
overwrites the oldest contents within the memory with new data as
storage limits are met, thereby conserving memory space.
[0058] Processor 48 controls telemetry interface 52 to send
pressure information to implantable stimulator 14 or programmer 16
on a continuous basis, at periodic intervals, or upon request from
the implantable stimulator or programmer. Wireless telemetry may be
accomplished by radio frequency (RF) communication or proximal
inductive interaction of pressure sensor 12 with programmer 16.
[0059] Power source 54 delivers operating power to the components
of implantable pressure sensor 12. Power source 54 may include a
battery and a power generation circuit to produce the operating
power. In some embodiments, the battery may be rechargeable to
allow extended operation Recharging may be accomplished through
proximal inductive interaction between an external charger and an
inductive charging coil within sensor 12. In some embodiments,
power requirements may be small enough to allow sensor 12 to
utilize patient motion and implement a kinetic energy-scavenging
device to trickle charge a rechargeable battery. In other
embodiments, traditional batteries may be used for a limited period
of time. As a further alternative, an external inductive power
supply could transcutaneously power sensor 12 whenever pressure
measurements are needed or desired.
[0060] FIG. 6 is a functional block diagram illustrating various
components of an implantable stimulator 14. In the example of FIG.
6, stimulator 14 includes a processor 56, memory 58, stimulation
pulse generator 60, telemetry interface 62, and power source 64.
Memory 58 stores instructions for execution by processor 56,
stimulation therapy data, and pressure information received from
pressure sensor 12 via telemetry interface. Pressure information is
received from pressure sensor 12 and may be recorded for long-term
storage and retrieval by a user, or adjustment of stimulation
parameters, such as amplitude, pulse width or pulse rate. Memory 58
may include separate memories for storing instructions, stimulation
parameter sets, and pressure information. Processor 56 controls
stimulation pulse generator 60 to deliver electrical stimulation
therapy and telemetry interface 62 to send and receive information.
An exemplary range of neurostimulation stimulation pulse parameters
likely to be effective in treating incontinence, e.g., when applied
to the sacral or pudendal nerves, are as follows:
[0061] 1. Frequency: between approximately 0.5 Hz and 500 Hz, more
preferably between approximately 5 Hz and 250 Hz, and still more
preferably between approximately 10 Hz and 50 Hz.
[0062] 2. Amplitude: between approximately 0.1 volts and 50 volts,
more preferably between approximately 0.5 volts and 20 volts, and
still more preferably between approximately 1 volt and 10
volts.
[0063] 3. Pulse Width: between about 10 microseconds and 5000
microseconds, more preferably between approximately 100
microseconds and 1000 microseconds, and still more preferably
between approximately 180 microseconds and 450 microseconds.
[0064] Based on pressure information received from sensor 12,
processor 56 interprets the information and determines whether any
therapy parameter adjustments should be made. For example,
processor 56 may compare the pressure level to one or more
thresholds, and then take action to adjust stimulation parameters
based on the pressure level. Information may be received from
sensor 12 on a continuous basis, at periodic intervals, or upon
request from stimulator 14 or external programmer 16.
Alternatively, or additionally, pressure sensor 12 may transmit
pressure information when there is an abrupt change in the pressure
level, e.g., at the onset of involuntary leakage.
[0065] In addition, processor 56 modifies parameter values stored
in memory 58 in response to pressure information from sensor 12,
either independently or in response to programming changes from
external programmer 16. Stimulation pulse generator 60 provides
electrical stimulation according to the stored parameter values via
a lead 15 implanted proximate to a nerve, such as a sacral nerve.
Processor 56 determines any parameter adjustments based on the
pressure information obtained form sensor 12, and loads the
adjustments into memory 58 for use in delivery of stimulation.
[0066] As an example, if the pressure information indicates an
inadequate sphincter closing pressure, processor 56 may increase
the amplitude, pulse width or pulse rate of the electrical
stimulation applied by stimulation pulse generator 60 to increase
stimulation intensity, and thereby increase sphincter closing
pressure. If sphincter closing pressure is adequate, processor 56
may implement a cycle of downward adjustments in stimulation
intensity until sphincter closing pressure becomes inadequate, and
then incrementally increase the stimulation upward until closing
pressure is again adequate. In this way, processor 56 converges
toward an optimum level of stimulation. Although processor 56 is
described in this example as adjusting stimulation parameters, it
is noted that the adjustments may be generated by external
programmer 16.
[0067] The adequacy of closing pressure is determined by reference
to the pressure information obtained from sensor 12. Sphincter
pressure may change due to a variety of factors, such as an
activity type, activity level or posture of the patient 18. Hence,
for a given set of stimulation parameters, the efficacy of
stimulation may vary in terms of sphincter pressure, due to changes
in the physiological condition of the patient. For this reason, the
continuous or periodic availability of pressure information from
implantable sensor 12 is highly desirable.
[0068] With this pressure information, stimulator 14 is able to
respond to changes in sphincter pressure with dynamic adjustments
in the stimulation parameters delivered to the patient 18. In
particular, processor 56 is able to adjustment parameters in order
to cause constriction of sphincter 22 and thereby avoid involuntary
leakage. In some cases, the adjustment may be nearly instantaneous,
yet prevent leakage. As an example, if patient 18 laughs, coughs,
or bends over, the resulted force on bladder 24 could overcome the
closing pressure of urinary sphincter 22. If pressure sensor 12
indicates an abrupt change in sphincter pressure, however,
stimulator 14 can quickly respond by more vigorously stimulating
the sacral nerves to increase sphincter closing pressure.
[0069] In general, if sphincter 22 is not constricting enough to
effectively close urethra 20, processor 56 may dynamically increase
the level of therapy to be delivered. Conversely, if sphincter 22
is consistently achieving effective constriction, processor 56 may
incrementally reduce stimulation, e.g., to conserve power
resources.
[0070] As in the case of sensor 12, wireless telemetry in
stimulator 14 may be accomplished by radio frequency (RF)
communication or proximal inductive interaction of pressure
stimulator 14 with implantable pressure sensor 12 or external
programmer 16. Accordingly, telemetry interface 62 may be similar
to telemetry interface 52. Also, power source 64 of stimulator 14
may be constructed somewhat similarly to power source 54. For
example, power source 64 may be a rechargeable or non-rechargeable
battery, or alternatively take the form of a transcutaneous
inductive power interface.
[0071] FIG. 7 is a schematic diagram illustrating cystoscopic
deployment of an implantable pressure sensor 12 via the urethra 20
using a deployment device 66. Pressure sensor 12 may be surgically
implanted. However, cystoscopic implantation via urethra is
generally more desirable in terms of patient trauma, recovery time,
and infection risk. In the example of FIG. 7, deployment device 66
includes a distal head 68, a delivery sheath 69 and a control
handle 70. Deployment device 66 may be manufactured from disposable
materials for single use applications or more durable materials for
multiple applications capable of withstanding sterilization between
patients.
[0072] As shown in FIG. 7, distal head 68 includes a cavity that
retains sensor housing 26 of implantable pressure sensor 12 for
delivery to a desired attachment site within bladder 24. Sensor
housing 26 may be held within cavity 72 by a friction fit, vacuum
pressure, or a mechanical attachment. In each case, once distal
head 68 reaches the attachment site, sensor housing 26 may be
detached. Sheath 69 is attached to distal head 68 and is steerable
to navigate urethra 20 and guide the distal head into position. In
some embodiments, sheath 69 and distal head 68 may include
cystoscopic viewing components to permit visualization of the
attachment site. In other cases, external visualization techniques
such as ultrasound may be used. Sheath 68 may include one or more
steering mechanisms, such as wires, shape memory components, or the
like, to permit the distal region adjacent distal head 68 to turn
abruptly for access to the mucosal lining of bladder 24.
[0073] A control handle 70 is attached to sheath 69 to aid the
physician in manually maneuvering deployment device 66 throughout
urethra 20 and bladder 24. Control handle 70 may have a one or more
controls that enable the physician to contort sheath 69 and allow
for deployment device 66 to attach pressure sensor housing 26 to
the mucosal lining of bladder 24 and then release the sensor
housing to complete implantation. A vacuum source 74 supplies
negative pressure to a vacuum line within sheath 69 to draw tissue
into the vacuum cavity defined by sensor housing 66. A positive
pressure source 76 supplies positive pressure to a drive a
fastening pin into the tissue captured in the vacuum cavity.
[0074] Deployment device 66 enters patient urethra 20 to deliver
pressure sensor 12 and implant it within bladder 24. First, the
physician must guide distal head 68 through the opening of urethra
20 in patient 18. Second, distal head 68 continues to glide up
urethra 20 and past the relaxed internal sphincter 22. Distal head
300 is then pushed through bladder neck 23 and into bladder 24, for
access to an appropriate site to attach pressure sensor 12. Using
actuators built into control handle 70, sheath 69 is bent to angle
distal head 68 into position. Again, sheath 69 may be steered using
control wires, shape memory alloys or the like.
[0075] As pressure sensor 12 is guided into place against the
mucosal wall 44 of bladder 24, a physician actuates control handle
70 to attach sensor 12 to mucosal wall 44 and then release the
attached sensor. Upon attachment, pressure sensor 12 is implanted
within bladder 24 of patient 18 and deployment device 66 is free to
exit the bladder. Exemplary methods for attachment and release of
sensor 12, including the use of both vacuum pressure and positive
pressure, will be described in greater detail below. Although FIG.
7 depicts cystoscopic deployment of pressure sensor 12, surgical or
laparoscopic implantation techniques alternatively may be used.
[0076] FIG. 8 is a schematic diagram illustrating retraction of
deployment device 66 upon fixation of pressure sensor 12 within the
urinary tract of patient 18. Once the sensor 12 is released,
optical fiber 28 remains attached to sensor housing 26. During
removal of deployment device 66, optical fiber 28 and flexible tube
section 30 maintain position within bladder neck 23 adjacent
sphincter 22. As deployment device 66 is removed, optical fiber 28
and flexible tube section 30 pass through a guide channel formed in
the deployment device. The guide channel ensures that optical fiber
28 and flexible tube section 30 remain pinned between distal head
68 and the wall of bladder 24.
[0077] As distal head 68 slides through sphincter 22 and urethra
20, however, optical fiber 28 releases from deployment device 66
and is left in place within the urethra in the region proximate
urinary sphincter 22. Deployment device 66 may then be completely
withdrawn past the external urinary sphincter and out of the
remainder of urethra 20. In the example of FIG. 8, optical fiber 28
is suspended by device housing 26, which is attached to mucosal
wall 44, and is held in place by pressure exerted against the
urethral wall by urinary sphincter 22. In other embodiments,
optical fiber 28 and flexible tube section 30 may be kept in place
using other techniques such as actively fixing optical fiber 28 or
tube section 30 to the side of urethra 20, e.g., with sutures or
other anchor mechanisms.
[0078] In a preferred embodiment, sheath 69 and distal head 68 may
be disposable. Disposable devices that come into contact with
patient 18 tissues and fluids greatly decrease the possibility of
infection in implantable devices. Control handle 70 does not come
into contact with body fluids of patient 18 and may be used for
multiple patients. In another embodiment, the entire deployment
device 66 may be manufactured out of robust materials intended for
multiple uses. The device would then need to be sterilizable
between uses. In still a further embodiment, the features of distal
head 68 may be incorporated into pressure sensor 12. In this
configuration, pressure sensor 12 may be larger in size but would
include the necessary elements for attachment within the device.
After attachment, the entire sensor would detach from sheath 69,
making removal of deployment device 66 easier on patient 18.
[0079] After the useful life of implantable pressure sensor 12 is
complete or it is no longer needed within patient 18, it can be
removed from patient 18 in some manner. As an example, deployment
device 66 may be reinserted into patient 18, navigated into bladder
24, and reattached to pressure sensor 12. Deployment device 66 may
then be withdrawn from the bladder 24 and urethra 20, explanting
sensor 12, including housing 26 and optical fiber 28, from patient
18. In another embodiment, as mentioned with respect to FIG. 3, the
attachment method of pressure sensor 12 to bladder 24 may involve
degradable materials, such as a biodegradable fixation pin. After a
certain period of time exposed to urine in the bladder 24, the
fixation material may structurally degrade and allow pressure
sensor 12 to be released from the mucosal wall 44 of bladder 24. In
some embodiments, sensor 12 may be sized sufficiently small to
follow urine out of the bladder, urethra, and body during a voiding
event. In other embodiments, sensor housing 26 or tube section 30
may carry a suture-like loop that can be hooked by a catheter with
a hooking element to withdraw the entire assembly from patient 18
via urethra 20. In still further embodiments, such a loop may be
long enough to extend out of the urethra, so that the loop can be
grabbed with an external device or the human hand to pull the
sensor 12 out of the patient.
[0080] FIG. 9 is a cross-sectional side view of distal head 68 of
deployment device 66 during deployment and fixation of pressure
sensor 12. In the example of FIG. 9, distal head 68 a vacuum line
78 and a positive pressure line 80. Vacuum line 78 is coupled to
vacuum source 74 via a tube or lumen extending along the length of
sheath 69. Similarly, positive pressure line 80 is coupled to
positive pressure source 76 via a tube or lumen extending along the
length of sheath 69. Vacuum line 78 is in fluid communication with
vacuum cavity 39, and permits the physician to draw a vacuum and
thereby capture a portion 42 of mucosal lining 44 within the vacuum
cavity. Positive pressure line 80 permits the physician to apply a
pulse of high pressure fluid, such as a liquid or a gas, to drive
fixation pin 46 into sensor housing 26 and through the portion 42
of mucosal lining 44. Pin 46 thereby fixes sensor housing 26 to
mucosal lining 44. In some embodiments, a membrane mounted over an
opening of positive pressure line 80 may be punctured by pin
46.
[0081] Optical fiber 28 resides within a channel of sheath 69 prior
to detachment or sensor 12 from distal head 68. Once fixation pin
46 attaches sensor 12 to bladder 24, vacuum line 78 is no longer
needed. However, in some embodiments, vacuum line 78 may be used to
detach pressure sensor 12 from distal head 68 of deployment device
66. By terminating vacuum pressure, or briefly applying positive
pressure through vacuum line 78, for example, head 68 may separate
from sensor 12 due to the force of the air pressure. In this
manner, vacuum line 78 may aid in detachment of sensor 12 prior to
withdrawal of deployment device 66.
[0082] As described previously in FIG. 3, fixation pin 46 punctures
mucosal lining 44 for fixation of sensor 12. While the force of
this fixation may vary with patient 18, deployment device 66
provides adequate force for delivery of pin 46. In an exemplary
embodiment, positive pressure line 80 is completely sealed and
filled with a biocompatible fluid, such as water, saline solution
or air. Sealing the end of positive pressure line 80 is a head 82
on fixation pin 46. Head 82 is generally able to move within
positive pressure line 80 much like a piston. Force to push
fixation pin 46 through the portion 42 of mucosal lining 44
captured in vacuum cavity 39 is created by application of a pulse
of increased fluid pressure within positive pressure line 80. For
example, the physician may control positive pressure source 76 via
control handle 70. This simple delivery method may provide high
levels of force, allow multiple curves and bends in articulating
arm 306, and enable a positive pressure line 80 of many shapes and
sizes.
[0083] In an alternative embodiment, a flexible, but generally
incompressible, wire may placed within positive pressure line 80
and used to force fixation pin 46 through the captured portion 42
of mucosal lining 44. This wire presents compressive force from
control handle 70 directly to the head 82 of fixation pin 46. This
method may eliminate any safety risk of pressurized fluids entering
patient 18 or, in some embodiments, permit retraction of pin 46
after an unsuccessful fixation attempt. The flexible wire may be
attached to pin 46 and pulled back to remove the pin from capture
mucosal tissue 42. The flexible wire may be sheared from fixation
pin 46 for detachment purposes as distal head 68 releases sensor
12. This detachment may be facilitated by a shearing element or
simply low shear stress of the wire enables separation when distal
head 68 slides past pin 46.
[0084] In FIG. 9, deployment device 66 illustrates optical fiber 28
on the same end of housing 26 as sheath 69, while the fixation
structures are located in the opposite, or distal end of distal
head 68. In some embodiments, it may be necessary for pressure
sensor 12 to be deployed with tube section 30 located at the distal
end of head 68 and the fixation structures located near sheath 69.
In still other embodiments, the fixation structures and tube
section 30 may be located on the same end of pressure sensor
12.
[0085] In some embodiments, deployment device 66 may include a
small endoscopic camera in the distal head 68. The camera may
enable the physician to better guide deployment device 66 through
urethra 20, past sphincter 22, and to a desired attachment location
of bladder 24 in less time with more accuracy. Images may be
displayed using video fed to a display monitor.
[0086] FIG. 10 is a cross-sectional bottom view of the deployment
device 66 of FIG. 10 before attachment of pressure sensor 12. As
shown in FIG. 10, distal head 68 includes proximal tube channel 84
to accommodate optical fiber 28 during placement of sensor 12 and
distal tube channel 86 to accommodate the flexible tube during
retraction of deployment device 66. In addition, sheath 69 includes
a sheath channel 88 to accommodate optical fiber 28 and flexible
tube section 30. Channels 84, 86, 88 serve to retain tube section
30 during delivery of sensor 12 to an attachment site. Note that
the channels are larger than the shown portion of optical fiber 28
to enable the passage of the larger perturbation section 30 of
optical fiber 28. In some embodiments, tube section 30 may be of
similar diameter to optical fiber 28.
[0087] Distal head 68 is rounded on both sides at the distal end to
permit easier entry of deployment device into areas of patient 18.
Head 68 may also be lubricated before delivery to facilitate ease
of navigation. On the proximal end of head 68, proximal tube
channel 84 runs through the head for unimpeded removal of optical
fiber 28 and tube section 30 during detachment of pressure sensor
12. This channel may be U-shaped, e.g. closed on 3 sides. In some
embodiments, proximal tube channel 84 may be an enclosed hole in
which optical fiber 28 resides and glides through upon deployment
device 30 removal.
[0088] Sheath channel 88 is formed within sheath 69 to allow
optical fiber 28 to stay in place during delivery of pressure
sensor 12. In this embodiment, optical fiber 28 is only partially
retained within channel 88. In some embodiments, sheath channel 88
may be deeper to allow optical fiber 28 to lie completely within
sheath 69, whereas others may include a completely enclosed channel
out of which optical fiber 28 glides after attachment.
[0089] Distal channel 86 in distal end of head housing 68 is not
used by optical fiber 28 before attachment. The purpose of this
open channel is to allow optical fiber 28 and flexible tube section
30 to glide through it while head 68 is removed from bladder 24. As
head 68 slides back past pressure sensor 12, optical fiber 28 and
tube section 30 will slide through channel 86 and head housing 68
will keep optical fiber 28 and tube section 30 between the wall of
bladder 24 and head 68 until head 68 has been removed beyond
sphincter 22. Optical fiber 28 and tube section 30 may then be
ensured correct placing through sphincter 22.
[0090] Some embodiments of optical fiber 28 and flexible tube
section 30 include multiple length and diameter combinations which
would lead to modifications in channels 84, 86 and 88. These
channels may be of different diameters or lengths to properly house
optical fiber 28, tube section 30, or both. One embodiment may
include flexible housing channels to accommodate a wide variety of
dimensions. Further embodiments of deployment device 30 may contain
modified channel locations in head housing 68. These locations may
be needed to place optical fiber 28 and flexible tube section 30 in
different locations, particularly at different sphincter sites as
in some embodiments.
[0091] FIG. 11 is a flow diagram illustrating a technique for
delivery of stimulation therapy based on closed loop feedback from
an implantable pressure sensor. In the example of FIG. 11,
implantable stimulator 14 requires information from implantable
pressure sensor 12 and external programmer 16. The flow of events
begins with implantable stimulator 14 communicating with
implantable pressure sensor 12 and sending a command to sense the
pressure of sphincter 22 (90). The pressure sensor 12 subsequently
acquires a pressure measurement and delivers the data to
implantable stimulator 14 (92). Upon receiving the pressure data,
implantable stimulator 14 calibrates the data and compares it to a
determined minimum pressure threshold (94).
[0092] If the measured pressure is higher than the threshold, the
loop begins again. If the pressure is lower than the threshold, the
flow continues to the next step of stimulation. Implantable
stimulator 14 communicates with external programmer 16 to check if
patient 18 has desired to void the contents of bladder 24 (96). If
patient 18 has signaled a voiding event, stimulation is skipped and
the process begins again. In the case of no voiding event desired,
sphincter 22 is not providing adequate closing pressure and needs
to be stimulated, or more vigorously stimulated. Implantable
stimulator 14 next performs the necessary tasks to adjust a level
of stimulation for stimulation pulse generator 60 (98). Stimulator
14 concludes the loop by delivering electric stimulation thereby to
a nerve that innervates sphincter 22 (100). After stimulation
therapy has commenced, the loop begins again to continue
appropriate therapy to patient 18.
[0093] In some embodiments, pressure sensor 12 may be used
exclusively for monitoring pressure without providing feedback for
stimulation therapy. In this case, the logic loop would be much
simpler and only include collecting data and sending it to an
external programmer (90 and 92). Pressure may be measured
continuously, intermittently or at the request of external
programmer 16. These embodiments may be used for disease diagnosis
or condition monitoring and may provide a patient to avoid frequent
clinic visits and uncomfortable procedures. In some embodiments,
the pressure measurements may form part of an automated voiding
diary that records voluntary voiding events, involuntary voiding
events, and urinary sphincter and urethral pressure levels prior
to, contemporaneous with, of after such an event.
[0094] Although the invention may be especially applicable to
sensing urinary sphincter pressure, the invention alternatively may
be applied more generally to other sphincters within the patient,
such as the lower esophageal sphincter (LES) or pyloric sphincter.
In addition, in those instances, the invention may be adapted to
support electrical stimulation of other body organs, such as the
stomach or intestines, e.g., for treatment of obesity or gastric
mobility disorders. Not only may stimulation of certain nerves
allow for the proper closure of a sphincter, but nerve stimulation
may be able to modify stomach contractions or intestinal
contractions based upon pressure measurements at those sites.
Pressure feedback from the implantable pressure sensor may be the
most effective therapy for some patients, e.g., in the form of
biofeedback that aids the patient in self-regulating bladder
control. Also, the invention need not be limited to
neurostimulation, and may be applied to stimulate other tissue,
including muscle tissue.
[0095] Various embodiments of the described invention may include
processors that are realized by microprocessors,
Application-Specific Integrated Circuits (ASIC), Field-Programmable
Gate Arrays (FPGA), or other equivalent integrated or discrete
logic circuitry. The processor may also utilize several different
types of data storage media to store computer-readable instructions
for device operation. These memory and storage media types may
include any form of computer-readable media such as magnetic or
optical tape or disks, solid state volatile or non-volatile memory,
including random access memory (RAM), read only memory (ROM),
electronically programmable memory (EPROM or EEPROM), or flash
memory. Each storage option may be chosen depending on the
embodiment of the invention. While the implantable stimulator and
implantable pressure sensor ordinarily will contain permanent
memory, a patient or clinician programmer may contain a more
portable removable memory type to enable easy data transfer for
offline data analysis.
[0096] Many embodiments of the invention have been described.
Various modifications may be made without departing from the scope
of the claims. For example, although the invention has been
generally described in conjunction with implantable
neurostimulation devices, a flexible tube sensor may also be used
with other implantable medical devices, such as electrical muscle
stimulation devices, functional electrical stimulation (FES)
devices, and implantable drug delivery devices, each of which may
be configured to treat incontinence or other conditions or
disorders. These and other embodiments are within the scope of the
following claims.
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